You are entitled to your opinion, no matter how wrong many of us think it is :)
> what would happen to the images after uploading?
I have no idea, as there is no such information given going as far as the upload form, nor in the FAQ. This is information you should provide.
Though that isn't the key problem IMO. For someone who backs out because of the sign-up requirement, you've wasted their time (and the service now has their images with no obvious pre-agreed policy covering re-use or other licensing issues).